The compound represented by the chemical formula (I) as will be specified later (hereunder referred to as “the compound (I)”) or a pharmaceutically acceptable salt thereof shows an α4-integrin-inhibitory action in vivo, it is a compound useful as a therapeutic agent for treating, for instance, inflammatory intestinal diseases and it can be produced according to the methods disclosed in Patent Documents 1 and 2 as will be specified below. In addition, there is reported, in Patent Document 3, an form a crystal or the like of the compound (I) as a form which is excellent in the storage stability and moisture-proofing characteristics. Moreover, Patent Document 4 reports that the solubility of the compound (I) can be improved by forming the compound (I), as a drug hardly soluble in water, into a solid dispersion, while it is maintained in its amorphous state.
On the other hand, it has also been known that if such a compound forms a salt, it may be, for instance, improved in its solubility and its bioavailability, as well as the modification of characteristics of the original compound or agent (see Non-Patent Document 1 specified below). However, there has not yet been reported any crystal of a pharmaceutically acceptable salt of the compound (I) and accordingly, there has been desired for the development of a crystalline salt of the compound (I) having excellent solubility in water, while maintaining the stability thereof sufficient for use in the production of a pharmaceutical preparations containing the same.